This invention relates to conductive coatings and specifically to a nonstick conductive coating for use with an electrosurgical cutting instrument.
Electrosurgical devices or surgical scalpels, which are adapted to use radio frequency electrical energy in the performance of hemostatic surgery, are disclosed in related commonly owned U.S. Pat. Nos. 4,232,676 to Herczog, and 4,248,231 to Herczog et al. Other such hemostatic surgical instruments are available in the prior art, for example, see U.S. Pat. No. Re. 29,088 for a heated surgical scalpel. There are other variations on the concept of hemostatic surgery including systems utilizing electric discharge to cut and cauterize, and related systems such as shown in U.S. Pat. Nos. 4,161,950, 4,033,351 and 3,913,583.
While the concept involved in the present invention might be adapted for use in many of the aforementioned electrosurgical devices, it is best exemplified for its usefulness in the cutting instruments of the type disclosed by Herczog et al. (hereinafter Herczog or RF blade). In one embodiment, currents are carried to separate electrodes which are desposited near the cutting edge of a glass or glass-ceramic material scalpel or blade. Moisture from incised tissue surfaces completes a circuit from one electrode to the other and the high frequency source generated currents pass through the tissue, generate heat and cause hemostasis in the vicinity of the electrodes.
In such a system it is possible for the blade to stick in the incision, thereby causing apparent dullness of the blade. The problem is alleviated when non-stick coatings are used, however, because of the nature of non-stick materials, many tend to be fragile and are abraded easily. Thus, the non-stick properties degrade in normal use, due in part to actual cutting, and partly due to the frequent wiping necessary in order to remove surgical debris adhered to the blade. When sticking is severe, the blade is unfit for further use and must be discarded. Further, when using the Herczog concept, the non-conductive nature of non-stick films tends to interfere with the conductivity of the electrodes.
There are a number of patents in the prior art disclosing non-stick coatings. These patents mainly relate to the use of fluorocarbon polymers on razor blades for increasing their lubricity and enhancing the comfort of such shaving instruments while in use. Such arrangements are described in U.S. Pat. Nos. 4,012,551 and 3,754,329. There is a copending patent application of R. E. Allen, Ser. No. 102,886, filed this same date and assigned to the assignee herein, disclosing conductive non-stick coatings applied to RF electrosurgical devices.
Allen's patent application teaches that the insulative nature of the non-stick materials normally interferes with the conductivity of the electrodes, but if the material is applied to textured electrodes and subsequently wiped away the surface of the electrode is free to conduct and the instrument exhibits non-stick characteristics. This occurs because the non-stick material permeates microscopic interstices in the electrode surface thereby providing a means for mechanical adherence of one to the other and the wiping step removes sufficient amounts of the insulative non-stick material from high profile points of the electrode surfaces to permit conduction. Allen discloses specific formulations of organic fluorocarbon materials such as those sold by E. I. DuPont de Nemours & Company under the registered trademark TEFLON.RTM..
The present invention discloses additional useful non-stick materials. While the non-stick coatings hereinafter described, at least partially fill microscopic irregularities or interstices in the conductive material, as in Allen, the materials selected for non-stick properties are believed to exhibit a surface effect or chemical bond with the instrument. The application of the chemically bonded non-stick materials does not require subsequent wiping to effect the required conductivity of the electrodes.